The mechanisms which mediate the formation and stability of intercellular attachments are critical to understanding both normal and aberrant developmental phenomena. The relative affinity of one cell for another is presumed to change during development such that cells form a continuum of differing architectural patterns with their neighbors culminating in morphology characteristic for a particular organ or tissue. In addition, changes in the adhesive capacity of neoplastic cells may be related to their ability to metastasize and invade surrounding tissue. The characteristics of the surface structures involved in the formation of adhesions, their synthesis and turnover are the objectives of this proposal.